Question

How does pyruvate turn into lactic acid?

Answer 1

We know that the muscles need the energy for its work and the movement also in the process of glycolysis, the glucose is converted into the pyruvate to store in the muscles. When there is the need for energy for the muscles, these pyruvates convert into lactic acid.

Complete answer:
The pyruvate is converted into the lactic acid in the muscle cells. In these cells, the pyruvate is obtained by the result of the glycolysis or the EMP pathway. This pyruvate accepts the electrons from the $NADH$ which is the electron donor and it is converted into the molecule of the lactic acid. Where after donating the electron, $NADH$ is converted into $NAD+$ ions. These obtained ions are useful in regenerating the glycolysis pathway to be continued under the anaerobic conditions. In this reaction, the electron is added to the molecule of the pyruvate and hence they are called the electron acceptor. This process involves the acceptance of the electron and the pyruvate is reduced to the lactic acid; with a carboxylic acid and a ketone functional group, pyruvic acid $\left( C{{H}_{3}}COCOOH \right)$ is the most basic of the alpha-keto acids. Pyruvic acid $\left( C{{H}_{3}}COCOOH \right)$ is an organic acid found in almost all living organisms. It ionizes to form hydrogen ions and an anion. This anion is known as pyruvate. Pyruvate and pyruvic acid are almost interchangeable terms among biochemists.
Therefore, pyruvate is reduced to lactate by the enzyme lactate dehydrogenase in the absence of oxygen. $NADH$ is oxidised to $NAD+$ in the reaction.

Note:
Remember that the Pyruvic acid is a central substance at the crossroads of carbohydrate, fat, and protein catabolism breaking down and anabolism synthesis protein catabolism breaking down and anabolism synthesis. Pyruvic acid may be made from glucose, converted back to carbohydrates such as glucose through gluconeogenesis.